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Message-Id: <20171011152059.2394516-2-arnd@arndb.de>
Date: Wed, 11 Oct 2017 17:20:13 +0200
From: Arnd Bergmann <arnd@...db.de>
To: Daniel Vetter <daniel.vetter@...ll.ch>,
Daniel Vetter <daniel.vetter@...el.com>,
Jani Nikula <jani.nikula@...ux.intel.com>,
Sean Paul <seanpaul@...omium.org>,
David Airlie <airlied@...ux.ie>
Cc: Arnd Bergmann <arnd@...db.de>, Dave Airlie <airlied@...hat.com>,
Chris Wilson <chris@...is-wilson.co.uk>,
Alex Deucher <alexander.deucher@....com>,
dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: [PATCH 2/2] drm: vblank: remove drm_timestamp_monotonic parameter
There is a risk of overflowing vblank timestamps in 2038 or 2106 if
someone sets the drm_timestamp_monotonic module parameter to zero.
I found no indication of anyone ever setting the parameter, or
complaining about the default being wrong, after it was introduced
as a way to handle backwards-compatibility with linux prior to
c61eef726a78 ("drm: add support for monotonic vblank timestamps"),
so it's probably safer to just remove the parameter completely
and only allowing the default behavior.
Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
drivers/gpu/drm/drm_internal.h | 1 -
drivers/gpu/drm/drm_ioctl.c | 2 +-
drivers/gpu/drm/drm_vblank.c | 29 ++++++-----------------------
3 files changed, 7 insertions(+), 25 deletions(-)
diff --git a/drivers/gpu/drm/drm_internal.h b/drivers/gpu/drm/drm_internal.h
index fbc3f308fa19..edd921adcf33 100644
--- a/drivers/gpu/drm/drm_internal.h
+++ b/drivers/gpu/drm/drm_internal.h
@@ -55,7 +55,6 @@ int drm_clients_info(struct seq_file *m, void* data);
int drm_gem_name_info(struct seq_file *m, void *data);
/* drm_vblank.c */
-extern unsigned int drm_timestamp_monotonic;
void drm_vblank_disable_and_save(struct drm_device *dev, unsigned int pipe);
void drm_vblank_cleanup(struct drm_device *dev);
diff --git a/drivers/gpu/drm/drm_ioctl.c b/drivers/gpu/drm/drm_ioctl.c
index a9ae6dd2d593..a78f03155466 100644
--- a/drivers/gpu/drm/drm_ioctl.c
+++ b/drivers/gpu/drm/drm_ioctl.c
@@ -235,7 +235,7 @@ static int drm_getcap(struct drm_device *dev, void *data, struct drm_file *file_
/* Only some caps make sense with UMS/render-only drivers. */
switch (req->capability) {
case DRM_CAP_TIMESTAMP_MONOTONIC:
- req->value = drm_timestamp_monotonic;
+ req->value = 1;
return 0;
case DRM_CAP_PRIME:
req->value |= dev->driver->prime_fd_to_handle ? DRM_PRIME_CAP_IMPORT : 0;
diff --git a/drivers/gpu/drm/drm_vblank.c b/drivers/gpu/drm/drm_vblank.c
index c605c3ad6b6e..810a93fc558b 100644
--- a/drivers/gpu/drm/drm_vblank.c
+++ b/drivers/gpu/drm/drm_vblank.c
@@ -82,20 +82,12 @@ drm_get_last_vbltimestamp(struct drm_device *dev, unsigned int pipe,
static unsigned int drm_timestamp_precision = 20; /* Default to 20 usecs. */
-/*
- * Default to use monotonic timestamps for wait-for-vblank and page-flip
- * complete events.
- */
-unsigned int drm_timestamp_monotonic = 1;
-
static int drm_vblank_offdelay = 5000; /* Default to 5000 msecs. */
module_param_named(vblankoffdelay, drm_vblank_offdelay, int, 0600);
module_param_named(timestamp_precision_usec, drm_timestamp_precision, int, 0600);
-module_param_named(timestamp_monotonic, drm_timestamp_monotonic, int, 0600);
MODULE_PARM_DESC(vblankoffdelay, "Delay until vblank irq auto-disable [msecs] (0: never disable, <0: disable immediately)");
MODULE_PARM_DESC(timestamp_precision_usec, "Max. error on timestamps [usecs]");
-MODULE_PARM_DESC(timestamp_monotonic, "Use monotonic timestamps");
static void store_vblank(struct drm_device *dev, unsigned int pipe,
u32 vblank_count_inc,
@@ -672,9 +664,6 @@ bool drm_calc_vbltimestamp_from_scanoutpos(struct drm_device *dev,
delta_ns = div_s64(1000000LL * (vpos * mode->crtc_htotal + hpos),
mode->crtc_clock);
- if (!drm_timestamp_monotonic)
- etime = ktime_mono_to_real(etime);
-
/* save this only for debugging purposes */
ts_etime = ktime_to_timespec64(etime);
ts_vblank_time = ktime_to_timespec64(*vblank_time);
@@ -694,11 +683,6 @@ bool drm_calc_vbltimestamp_from_scanoutpos(struct drm_device *dev,
}
EXPORT_SYMBOL(drm_calc_vbltimestamp_from_scanoutpos);
-static ktime_t get_drm_timestamp(void)
-{
- return drm_timestamp_monotonic ? ktime_get() : ktime_get_real();
-}
-
/**
* drm_get_last_vbltimestamp - retrieve raw timestamp for the most recent
* vblank interval
@@ -738,7 +722,7 @@ drm_get_last_vbltimestamp(struct drm_device *dev, unsigned int pipe,
* Return current monotonic/gettimeofday timestamp as best estimate.
*/
if (!ret)
- *tvblank = get_drm_timestamp();
+ *tvblank = ktime_get();
return ret;
}
@@ -811,8 +795,8 @@ static void send_vblank_event(struct drm_device *dev,
e->event.sequence = seq;
/*
* e->event is a user space structure, with hardcoded unsigned
- * 32-bit seconds/microseconds. This will overflow in 2106 for
- * drm_timestamp_monotonic==0, but not with drm_timestamp_monotonic==1
+ * 32-bit seconds/microseconds. This is safe as we always use
+ * monotonic timestamps since linux-4.15
*/
e->event.tv_sec = tv.tv_sec;
e->event.tv_usec = tv.tv_nsec / 1000;
@@ -899,7 +883,7 @@ void drm_crtc_send_vblank_event(struct drm_crtc *crtc,
} else {
seq = 0;
- now = get_drm_timestamp();
+ now = ktime_get();
}
e->pipe = pipe;
e->event.crtc_id = crtc->base.id;
@@ -1408,9 +1392,8 @@ static void drm_wait_vblank_reply(struct drm_device *dev, unsigned int pipe,
/*
* drm_wait_vblank_reply is a UAPI structure that uses 'long'
- * to store the seconds. This will overflow in y2038 on 32-bit
- * architectures with drm_timestamp_monotonic==0, but not with
- * drm_timestamp_monotonic==1 (the default).
+ * to store the seconds. This is safe as we always use monotonic
+ * timestamps since linux-4.15.
*/
reply->sequence = drm_vblank_count_and_time(dev, pipe, &now);
ts = ktime_to_timespec64(now);
--
2.9.0
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